Oscillation/Vibration in lathe

[calgaryguy]

Another post about my Standard Modern 9" lathe:

While running in some speeds and most noticeably in the two highest speed settings, I can feel and hear (if I listen closely) a oscillation/vibration in somewhere in the gear works.

I've been working on getting my tailstock aligned, and with a dial indicator touching the tailstock, I can see a ~.005 harmonic/oscillation/vibration occur. I'm wondering what effect this might have on my lathe accuracy. I realize this is a ~50+ year old lathe (guessing), and some wear/imbalance is to be expected.

I'm trying to get a video either linked or uploaded.

EDIT: Video No Sound. Converting from .mov (iphone) to mp4 seems to have stripped the sound. THere is a very very slight audible harmonic noise that aligns with the dial indicator oscillation. If I put the palm of my hand against the gearbox/headstock I can also feel a very slight oscillating harmonic

 

[calgaryguy]

I should add that this Harmonic/Oscillation is most prominent when running at the '900 RPM' gearbox/belt setting.

 

[YYCHM]

Try lifting the motor and see if the vibration diminishes. My machine is belt tension sensitive. I find that the looser I make the belt the better.

9" SM Utilathe Restoration

Hatched another birds nest today :rolleyes: Man, those things just materialize in the blink of an eye. Ya, I know, we have had this discussion already.

canadianhobbymetalworkers.com

 

[calgaryguy]

I've been wondering about that. I've got mine setup with the spring tensioner. I'm also using a 'Powertwist' link belt instead of a traditional rubber belt. They usually run smoother than a traditional belt and you never have worries about the belt taking a 'set' if left unused for a few months.

 

[YYCHM]

I've been wondering about that. I've got mine setup with the spring tensioner. I'm also using a 'Powertwist' link belt instead of a traditional rubber belt. They usually run smoother than a traditional belt and you never have worries about the belt taking a 'set' if left unused for a few months.

The powertwist is good, I went with one as well. Keep that.

 

[jcdammeyer]

Too many variables in that video. It's possible that the long shaft isn't clamped 'correctly' in the chuck and that it's just off center enough (from wear in one of the jaws) that the shaft is telescoping vibration to the tail stock.

Start with no chuck. No work. Put the dial indicator on the headstock and on the tailstock and see if the vibration is still there. What does it feel like when there's no chuck.

Then put the chuck on, close the jaws all the way and do the test again.

Next put a short piece of stock in the chuck, center drill for the tailstock and then replace the drill with the center and check if there is vibration.

Is your lathe bed level. I just went through that. True, a twisted bed will only pivot the tail stock so you'd get taper but it also pivots over an arc. That means the end away from the chuck is no longer in line with the chuck but off center.

If you were turning this long shaft between centers you wouldn't see a problem but the chuck is trying to hold the stock straight out while the tail stock is pulling it over.

Just some ideas.

 

[calgaryguy]

Too many variables in that video. It's possible that the long shaft isn't clamped 'correctly' in the chuck and that it's just off center enough (from wear in one of the jaws) that the shaft is telescoping vibration to the tail stock.

Start with no chuck. No work. Put the dial indicator on the headstock and on the tailstock and see if the vibration is still there. What does it feel like when there's no chuck.

Then put the chuck on, close the jaws all the way and do the test again.

Next put a short piece of stock in the chuck, center drill for the tailstock and then replace the drill with the center and check if there is vibration.

Is your lathe bed level. I just went through that. True, a twisted bed will only pivot the tail stock so you'd get taper but it also pivots over an arc. That means the end away from the chuck is no longer in line with the chuck but off center.

If you were turning this long shaft between centers you wouldn't see a problem but the chuck is trying to hold the stock straight out while the tail stock is pulling it over.

Just some ideas.

The oscillation is present with nothing chucked in the lathe. This is the first time I've been able to *show* it on video via the dial indicator needle bouncing.

I was planning to swap in the 4 jaw chuck I have and see if that changes things. Both the 3 jaw and 4 jaw have backing plates, and both are aligned per the previous owners (SAIT College I assume) markings.

My lathe bed is 'level'
from a flat to the world perspective: I've used a 6" starrett machinists level and levelled the lathe end to end and front to back within .0015
from a alignment perspective: I've turned a 6" shaft and measured taper in it, and added shims under the tailstock end of the lathe bed(not under the tailstock itself) until my taper measured over 6" was about .0005-.001. I couldnt get it any better than this - I suspect a bit of wear in teh ways.

 

[YYCHM]

The oscillation is present with nothing chucked in the lathe. This is the first time I've been able to *show* it on video via the dial indicator needle bouncing.

I was planning to swap in the 4 jaw chuck I have and see if that changes things. Both the 3 jaw and 4 jaw have backing plates, and both are aligned per the previous owners (SAIT College I assume) markings.

What's the run out on the 3J?

Try running it with out a chuck and see what the vibration is like.

 

[jcdammeyer]

Remove the chuck and see if the vibration is still there.

 

[calgaryguy]

What's the run out on the 3J?

Measured where?

per my post I just added (prolly after you replied):

"
My lathe bed is 'level':
from a flat to the world perspective: I've used a 6" starrett machinists level and levelled the lathe end to end and front to back within .0015
from a alignment perspective: I've turned a 6" shaft and measured taper in it, and added shims under the tailstock end of the lathe bed(not under the tailstock itself) until my taper measured over 6" was about .0005-.001. I couldnt get it any better than this - I suspect a bit of wear in teh ways.
"

 

[calgaryguy]

So before I dig deeper into this oscillation, its probably useful to ask "is it uncommon/rare for a lathe to have any sort of oscillation/harmonic?". I dont know whats normal and what isnt. Especially considering I have a 50plus year old lathe. And its a light duty lathe to boot (less cast to dampen harmonics I would suppose).

 

[jcdammeyer]

My Southbend with ribbed belt stitched together with mig wire makes a once per belt rev ticking. There's a certain amount of what you could call vibration on the tail stock at 1829 RPM. But when you look at the belt from motor to 3 step flat belt pulley along with possibly out of balance pulleys I don't find the vibration overly onerous.

 

[YYCHM]

Measured where?

per my post I just added (prolly after you replied):

"
My lathe bed is 'level':
from a flat to the world perspective: I've used a 6" starrett machinists level and levelled the lathe end to end and front to back within .0015
from a alignment perspective: I've turned a 6" shaft and measured taper in it, and added shims under the tailstock end of the lathe bed(not under the tailstock itself) until my taper measured over 6" was about .0005-.001. I couldnt get it any better than this - I suspect a bit of wear in teh ways.
"

LOL.... You actually managed to use that 6" starrett machinist level? I borrow one from @RobinHood and found it way too sensitive to do anything with.

Chuck something up in the 3J that you know is round (I use the shank from a broken 3/8" end mill) and measure the runout close to the chuck jaws. I just reset my 3J on it's back plate yesterday. It had developed 7 thou run out. I can get that down to 1/2 a thou by tapping the chuck over relative to the back plate.

I don't think this has anything to do with the vibration you're seeing.

 

[calgaryguy]

My Southbend with ribbed belt stitched together with mig wire makes a once per belt rev ticking. There's a certain amount of what you could call vibration on the tail stock at 1829 RPM. But when you look at the belt from motor to 3 step flat belt pulley along with possibly out of balance pulleys I don't find the vibration overly onerous.

Do you think the vibration you experience affects your cut/finish quality or accuracy of cuts?

 

[YYCHM]

So before I dig deeper into this oscillation, its probably useful to ask "is it uncommon/rare for a lathe to have any sort of oscillation/harmonic?". I dont know whats normal and what isnt. Especially considering I have a 50plus year old lathe. And its a light duty lathe to boot (less cast to dampen harmonics I would suppose).

Not uncommon for this class of machine. If you were to step up to a 11" or 13" you would see a significant difference.

 

[calgaryguy]

LOL.... You actually managed to use that 6" starrett machinist level? I borrow one from @RobinHood and found it way too sensitive to do anything with.

I had to machine 4 'feet' for my lathe cabinet from 3" solid bar, 2" thick with a levelling screw recess machined into each in order to be able to get any sort of fine adjustment and accuracy in the adjustments on the lathe cabinet adjusting screws. I can post pics if you like of the installed 'feet'. When the levelling screws were set straight on the concrete floor, adjusting the screws would either a) 'walk' the lathe cabinet around slightly as they turned, or b) seemingly dig into the concrete a little.

 

[YYCHM]

I had to machine 4 'feet' for my lathe cabinet from 3" solid bar, 2" thick with a levelling screw recess machined into each in order to be able to get any sort of fine adjustment and accuracy in the adjustments on the lathe cabinet adjusting screws. I can post pics if you like of the installed 'feet'. When the levelling screws were set straight on the concrete floor, adjusting the screws would either a) 'walk' the lathe cabinet around slightly as they turned, or b) seemingly dig into the concrete a little.

Post away, I'm interested in your levelers. Basically what I concluded from playing with @RobinHood 's machinist level. Fine adjusters were in order, but, that's not practical in my case.

 

[jcdammeyer]

Do you think the vibration you experience affects your cut/finish quality or accuracy of cuts?

I'm happy with what I get but whether it matches someone else's standards I don't know. Could be that my cuts are garbage but I'm not clever enough to know.

 

[YYCHM]

I dont know whats normal and what isnt.

Like you, I didn't know what was normal and what wasn't when I got my Utilathe. The first time I saw @RobinHood 's 13" (or was it 11"?) in action I went Ahhhhh I see.

@Janger is really close to you. Have him show you what his machine exhibits for vibration etc. AND he's got a really cool CNC mill.

@Johnwa isn't that far away from you either. You could see how his Utilathe and South Bend behave.

The absolute smoothest machine I have seen so far is @eotrfish 's Emco.

 

[YYCHM]

Try this.... I just discovered I can displace the tail stock a thou just by pulling the chuck through by hand???? At 900 RPM I'm seeing a 2 thou flutter at the tail stock. The displacement is being measured between the bench and the tail stock, so I question if that really means anything.